The European Butterfly Indicator for
Grassland species: 1990-2009
The European Butterfly Indicator
for Grassland species: 1990-2009
The European Butterfly Indicator for Grassland species 1990-2009
Acknowledgements
Special thanks goes to all the volunteers for their data collection. They are vital in producing
overviews and indicators on the state of Europe’s butterflies.
Authors
Chris van Swaay, Arco van Strien, Alexander Harpke, Benoît Fontaine, Constantí Stefanescu, David
Roy, Dirk Maes, Elisabeth Kühn, Erki Õunap, Eugenie Regan, Giedrius Švitra, Janne Heliölä, Josef
Settele, Martin Warren, Matthias Plattner, Mikko Kuussaari, Nina Cornish, Patricia Garcia Pereira,
Patrick Leopold, Reinart Feldmann, Romain Jullard, Rudi Verovnik, Sergey Popov, Tom Brereton,
Adriaan Gmelig Meyling, Sue Collins
Commissioner
This study/report was funded by and is the property of the European Environment
Agency (EEA). The opinions expressed therein are those of the Contractor only and do not represent
the Agency’s official position.
Production
De Vlinderstichting, P.O. Box 506, NL-6700 Wageningen, Netherlands, www.vlinderstichting.nl
Butterfly Conservation Europe, www.bc-europe.eu
Statistics Netherlands, www.cbs.nl
Preferred citation
Van Swaay, C.A.M., Van Strien, A.J., Harpke, A., Fontaine, B., Stefanescu, C., Roy, D., Maes, D., Kühn,
E., Õunap, E., Regan, E., Švitra, G., Heliölä, J., Settele, J., Warren, M.S., Plattner, M., Kuussaari, M.,
Cornish, N., Garcia Pereira, P., Leopold, P., Feldmann, R., Jullard, R., Verovnik, R., Popov, S., Brereton,
T., Gmelig Meyling, A., Collins, S. (2010). The European Butterfly Indicator for Grassland species 19902009. Report VS2010.010, De Vlinderstichting, Wageningen
Keywords:
Butterfly, Monitoring, Trend, Index, Europe, European Union, Indicator, Biodiversity
May 2010
The Mazarine Blue (Cyaniris semiargus) is a
typical butterfly of semi-natural grasslands.
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Contents
Summary ................................................................................................................................................. 3
Chapter 1 / Introduction ......................................................................................................................... 4
Chapter 2 / Building the European Grassland Butterfly Indicator .......................................................... 6
Fieldwork .............................................................................................................................................. 6
Population trend .................................................................................................................................. 7
Chapter 3 / Species trends ...................................................................................................................... 8
Chapter 4 / The indicator ...................................................................................................................... 11
Chapter 5 / Drivers behind the changes in grassland butterflies .......................................................... 12
Chapter 6 / Implications ........................................................................................................................ 15
What does the European Grassland Butterfly Indicator tell us? ....................................................... 15
Can the trend be reversed? ............................................................................................................... 16
Butterflies as indicators ..................................................................................................................... 18
Chapter 7 / How to continue with monitoring and indicator production?........................................... 19
Chapter 8 / Conclusions ........................................................................................................................ 20
Literature ............................................................................................................................................... 21
Annex I / Butterfly Monitoring Schemes in the indicator ..................................................................... 23
Annex II / Method ................................................................................................................................. 25
Annex III / Improving the indicator and building other butterfly indicators......................................... 27
The Large Skipper (Ochlodes sylvanus) is a
widespread and common butterfly in most of
Europe.
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2
Summary

This report presents the third version of
the European Grassland Butterfly
Indicator, one of the indicators for
biodiversity in the SEBI2010 (Streamlining
European 2010 Biodiversity Indicators), a
pan-European initiative led by the
European Environment Agency.

Abandonment is caused by socioeconomic factors. When farming of low
productivity land brings low incomes,
young farmers leave their villages and the
land is left unmanaged. The grassland
quickly becomes tall and rank and is soon
replaced by scrub and woodland.

The indicator is based on national
Butterfly Monitoring Schemes in fifteen
countries from all over Europe, most of
them active in the European Union


The indicator shows that since 1990,
butterfly populations have declined by
almost 70%, indicating a dramatic loss of
grassland biodiversity. This also means the
situation has not improved since the
previous version of the indicator.
The implementation of the Natura 2000
areas will be most beneficial in the
intensified parts of Europe, especially
North-west Europe, whereas the support
of High Nature Value farmland is vital to
stop abandonment, especially in Eastern
and Southern Europe.

Butterflies belong to the few species
groups for which European wide
monitoring is possible. Therefore butterfly
monitoring and the building of indicators
on a regular basis should be endorsed by
the EU and its member states.

Butterflies offer the possibility to be used
as a structural headline indicator, not only
for grasslands, but also for other habitats
and pressures such as climate change.



Of the seventeen species, ten have
declined in Europe and two have
remained stable. For five species the trend
is uncertain.
The main driver behind the decline of
grassland butterflies is the change in rural
land use: agricultural intensification where
the land is relatively flat and easy to
cultivate, abandonment in mountains and
wet areas, mainly in Eastern and Southern
Europe.
Agricultural intensification leads to
uniform, almost sterile grasslands, where
the management is so intensive that
grassland butterflies can only survive in
traditional farmed low input systems (High
Nature Value Farmland) as well as nature
reserves, and marginal land such as road
verges and amenity areas.
140
Butterfly Conservation Europe / Statistics Netherlands
120
100
80
60
40
20
0
1990
1994
1998
2002
2006
2010
The European Grassland Butterfly Indicator
shows a dramatic decline of almost 70%.
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Chapter 1 / Introduction
This is the third version of the European Grassland Butterfly Indicator. It is based
on the population trends of seventeen butterfly species in fifteen countries. As
more and more countries develop robust monitoring schemes, the relevance of
butterflies as European biodiversity indicators grows.
The European Union and its member states
are committed to halting the loss of
biodiversity across Europe by 2010. This is
complemented by a target to significantly
reduce the global rate of biodiversity loss by
2010. These targets are accompanied by a
growing consensus on the need for structured
European coordination of biodiversity
monitoring, indicators, assessment and
reporting efforts, with a long-term perspective
and a sound funding basis.
In this report we give an overview of the
trends of seventeen grassland butterflies in
Europe and the European Union. Furthermore
these trends are combined to produce a
European Grassland Butterfly Indicator. This
indicator is one of the 26 headline indicators
for inclusion in the set of European
biodiversity indicators (European Environment
Agency, 2007), and will be used in the 2010
Assessment Report on Biodiversity in the panEuropean region.
The Small Blue (Cupido minimus) is indeed one of the
smallest European butterflies. It’s a specialist species of
calcareous grasslands.
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Butterfly monitoring enjoys a growing
popularity in Europe. Map 1 shows the current
Butterfly Monitoring Schemes (BMS) and the
countries where they are expected soon.
Although Butterfly Monitoring Schemes are
present in a growing number of countries and
new ones are being initiated in many places,
long time-series are only available for a
limited number of countries. For this new
indicator data were used from 15 countries:
Belgium, Estonia, Finland, France, Germany,
Ireland, Lithuania, Jersey, Portugal, Slovenia,
Spain, Switzerland, The Netherlands, Ukraine
and the United Kingdom. Andorra is included
in the Catalonian (Spanish) scheme.
In this report we update the European
Grassland Butterfly Indicator, first published
by Van Swaay & Van Strien in 2005. The
updated indicator not only has a longer timeseries, with data from the 2005-2009 field
seasons now included, but also the method of
calculating the indicator has been improved
and enhanced. Furthermore three new
countries have been added.
The method closely follows the one for the
bird indicators (Gregory et al., 2005).
Map 1: Countries contributing their
data to the European Grassland
Butterfly Indicator:
Belgium (Flanders): since 1991
Estonia: since 2004
Finland: since 1999
France: since 2005 (Doubs area 20012004)
Germany: since 2005 (NordrheinWestfalen since 2001, Pfalz-region for
P. nausithous since 1989)
Ireland: since 2007
Lithuania: since 2009
Jersey: since 2004
Portugal:1998-2006
Slovenia: since 2007
Spain (Catalonia, including Andorra):
since 1994
Switzerland (Aargau): since 1998
The Netherlands: since 1990
Ukraine (Transcarpathia): since 1990
United Kingdom: since 1976
In 2009 more than 3000 transects
were counted.
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Chapter 2 / Building the European Grassland Butterfly Indicator
The European Grassland Butterfly Indicator shows the population
trend of butterflies which are characteristic for grasslands in Europe.
Fieldwork
The Butterfly Indicator is based on the fieldwork
of thousands of trained professional and
volunteer recorders, counting butterflies on
more than 3000 transects scattered widely
across Europe (see map 1). These counts are
made under standardised conditions. National
coordinators collect the data and perform the
first quality control. More details can be found in
Annex I.
Grassland butterflies
The same selection of grassland butterflies was
used as in the previous two versions of this
indicator. European butterfly experts selected
species they considered to be characteristic of
European grassland and which occurred in a
large part of Europe, covered by the majority of
the Butterfly Monitoring Schemes and having
grasslands as their main habitat (Van Swaay et
al., 2006). The species are listed in figure 1.
Butterflies are recorded along transects. Most
of these counts are done by volunteers, who
are vital to the Butterfly Monitoring Schemes
and to produce the indicator.
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Widespread
Grassland
butterflies
Widespread species: Ochlodes sylvanus, Anthocharis cardamines, Lycaena phlaeas, Polyommatus icarus,
Lasiommata megera, Coenonympha pamphilus and Maniola jurtina
Specialist
Grassland
Butterflies
Specialist species: Erynnis tages, Thymelicus acteon, Spialia sertorius, Cupido minimus, Phengaris arion,
Phengaris nausithous, Polyommatus bellargus, Cyaniris semiargus, Polyommatus coridon and
Euphydryas aurinia
Figure 1: Seventeen butterflies were used to build The European Grassland Butterfly Indicator,
comprising seven widespread and ten specialist species.
Population trend
National population trends from the Butterfly
Monitoring Schemes (map 1), calculated by the
program TRIM (Pannekoek & Van Strien, 2003)
are combined to form supra-national species
trends (chapter 3). These trends per butterfly
species are then combined into an indicator: a
unified measure of biodiversity following the
bird indicators as described by Gregory et al.
(2005), by averaging indices of species rather
than abundances in order to give each species an
equal weight in the resulting indicators. When
positive and negative changes of indices are in
balance, then we would expect their mean to
remain stable. If more species decline than
increase, the mean should go down and vice
versa. Thus, the index mean is considered a
measure of biodiversity change.
More details on the method can be found in the
report of the previous indicator (Van Swaay &
Van Strien, 2008). Although the Butterfly
Monitoring Schemes are very similar, there are
differences in choice of location, number of
counts, etc. These are summarised in Annex 1.
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Chapter 3 / Species trends
The European Grassland Butterfly Indicator is built from European species trends. In
this chapter, we give an overview of the trends of grassland butterflies in Europe and
the EU.
First, we calculate the trend in each country and
for each species separately. Figure 2 shows four
of the national trends for the Wall Brown
(Lasiommata megera). The European trend is
calculated for this species by combining all the
national trends (figure 2). The results show that
this butterfly declined in the 1990s, had a few
better years around 2000, but declined again
since then. Table 1 shows the trend for the 17
individual species of the indicator, both in the EU
and in Europe as a whole. In Europe ten species
are declining and two are stable. The trend for
the remaining species is uncertain. In the EU,
eight species show a decline and five are stable.
For four species the trend is uncertain. No
species show a significant increase.
175
France
The Netherlands
Spain - Catalonia
United Kingdom
Index (first year=100)
150
125
100
75
50
25
0
1990
1994
1998
2002
2006
2010
120
100
Index (1990=100)
Figure 2: National and European trends for the
Wall Brown (Lasiommata megera).
The upper graph shows the trend for four selected
Butterfly Monitoring Schemes. Note that the
starting year (see also map 1) for each scheme is
different. All indexes are set to 100 for the first year
of a scheme.
The lower graph shows the European trend,
resulting from the four Butterfly Monitoring
Schemes in the upper graph plus nine other
countries.
80
60
40
20
0
1990
1994
1998
2002
2006
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2010
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Table 1: Supra-national trends of the 17 butterfly species of the
European Grassland Butterfly Indicator. For the trend
classification see annex II.
Species
Phengaris nausithous
Erynnis tages
Lasiommata megera
Lycaena phlaeas
Thymelicus acteon
Ochlodes sylvanus
Coenonympha pamphilus
Cupido minimus
Anthocharis cardamines
Polyommatus icarus
Maniola jurtina
Polyommatus coridon
Cyaniris semiargus
Polyommatus bellargus
Spialia sertorius
Euphydryas aurinia
Phengaris arion
Trend in Europe
decline
decline
decline
decline
decline
decline
decline
decline
decline
decline
stable
stable
uncertain
uncertain
uncertain
uncertain
uncertain
Trend in EU
decline
decline
decline
decline
decline
decline
decline
decline
stable
stable
stable
stable
stable
uncertain
uncertain
uncertain
uncertain
When interpreting the species trends it is
important to realise that:
 The coverage of the species’ populations and
thus the representativeness of the data may
be lower at the beginning of the time series
(see also map 1). As more countries join in
later, the indices improve in accuracy each
year.
 Large year to year fluctuations or a low
number of transects, can cause large
standard errors, leading to uncertain
European or EU trends.
 In half of the EU countries, and even more
non-EU countries, there is no Butterfly
Monitoring Scheme yet. The trends shown
only represent the countries in map 1.
However, because they are based on a wide
range of countries, we believe that they are
reasonably representative of Europe as a
whole.
Figure 3 shows some examples of European
Butterfly trends:
 The Dingy Skipper (Erynnis tages), a brown
butterfly with a preference for nutrient
poor, often dry grasslands.
 The Meadow Brown (Maniola jurtina), a
widespread and in many countries very
common and abundant butterfly, occurring
on all kinds of grasslands.
 The Marsh Fritillary (Euphydryas aurinia), a
specialist species of both wet meadows and
calcareous grasslands.
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120
Index (1990=100)
100
80
60
40
20
0
1990
1994
1998
2002
2006
2010
160
Index (1990=100)
140
120
100
80
60
40
20
0
1990
1994
1998
2002
2006
2010
1994
1998
2002
2006
2010
250
Index (1990=100)
200
150
100
50
0
1990
Figure 3: European trends of three butterflies in Europe.
Top: The Dingy Skipper (Erynnis tages) shows a significant decline, in spite of year to year fluctuations.
Middle: The Meadow Brown (Maniola jurtina) is considered stable, in spite of a short term peak in 1991 and 1992.
Bottom: Large fluctuations make the trend of the Marsh Fritillary (Euphydryas aurinia) uncertain.
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Chapter 4 / The indicator
The European Grassland Butterfly Indicator has been updated both for Europe and
for the EU. In this chapter both indicators are presented.
little in the last few years, it has not stopped. So
far 2008 was the worst year for these butterflies,
both on a European and EU scale. The negative
trend in the EU countries alone is a little less
than in Europe as a whole, with a decline of
almost 60% over the period . As discussed in the
new Red List of European Butterflies (Van Swaay
et al., 2010), this might be due to the fact that
the large decline of butterflies in NW Europe
(countries all already in the EU for a long time)
happened before 1990.
Figure 4 shows the European Grassland Butterfly
Indicator, as well as the indicator for the
countries of the EU alone. The indicator is based
on the supra-national species trends as
presented in chapter 3. As in previous versions,
both indicators showed a marked decline
between 1990 and 2009. Compared to 1990, the
European populations of the 17 indicator species
have declined by, on average, almost 70%.
Although the decline seems to have slowed a
140
140
Butterfly Conservation Europe / Statistics Netherlands
Butterfly Conservation Europe / Statistics Netherlands
120
120
100
100
80
80
60
60
40
40
20
20
0
0
1990
1994
1998
2002
2006
2010
1990
1994
1998
2002
2006
2010
Figure 4: The Grassland Butterfly Indicators for Europe (left) and the EU (right).
The indicators are based on the countries in map 1 and characteristic grassland butterfly species in figure 1.
Both indicators show a marked decline of the population sizes of the 17 species.
DE VLINDERSTICHTING 2010 | The European Butterfly Indicator for Grassland species 1990-2009
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Chapter 5 / Drivers behind the changes in grassland butterflies
Grassland butterflies have undergone a huge overall decrease in numbers. Their
populations declined by almost 70% from 1990 to 2009. Although the causes for the
decline are different for each species and country, the two main drivers are
agricultural intensification and abandonment.
Large parts of Europe are used for agricultural
purposes, and grasslands are a major land-cover
type within these areas. For centuries,
grasslands have formed an important part of the
European landscape. Sustainably managed seminatural grassland harbours a high biodiversity,
especially of plants, butterflies and many other
insect groups.
Grasslands are the main habitat for many
European butterflies. Out of 436 butterfly
species in Europe for which information on
habitat type is available, 382 (88%) occur on
grasslands in at least one country in Europe, and
for more than half of the species (280 species,
57%) grassland is their main habitat. The most
species-rich biotopes in Europe are dry
grasslands: dry calcareous grasslands and
steppes (274 butterfly species), alpine and
subalpine grasslands (261), mesophile grasslands
(223) and dry siliceous grasslands (220 species)
(Van Swaay et al., 2006).
Thomas (2005) argued that butterflies are good
indicators of insects, which comprise the most
species rich group of animals in Europe. The
trend in grassland butterflies is thus an indicator
for the health of grassland ecosystems and their
component biodiversity. Insects play a crucial
role in pollination services and the health of the
ecosystems on which they depend is important
for Europe’s future economic and social
wellbeing.
In most of Europe, grasslands are not the climax
vegetation. Without any form of management,
they would gradually change into scrub and
forest. This means that grasslands and their
butterflies are highly dependent on activities
such as grazing or mowing. Traditional forms of
farming management, such as extensive
livestock grazing and hay-making where fertiliser
and pesticide use are minimal, provide an ideal
environment for these butterflies.
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Until a few decades ago, semi-natural grasslands
were widespread and common all over the
continent. Since the 1950s grassland
management has undergone huge changes. In
North-western Europe, farming has intensified
rapidly and over the last fifty years semi-natural
grasslands have become greatly reduced in area.
In some countries they are more or less confined
to nature reserves or protected areas. In Eastern
and Southern Europe semi-natural grasslands
remained a part of the farming system until
more recently. However, in the last few decades,
these are also being lost and there has been a
clear development towards intensification,
especially on relatively flat and nutrient rich
places. In contrast, steeper and less productive
areas have tended to become abandoned. The
effects of intensification and abandonment on
traditional grassland are:

Intensification
Intensification comprises a wide range of
activities, including the conversion of
unimproved grasslands to arable crops,
heavy use of fertilisers, drainage, the use of
herbicides, insecticides and pesticides,
enlargement of fields, and the use of heavy
machines. In its most extreme form (e.g. in
the Netherlands and Flanders, Maes & Van
Dyck, 2001) the remaining agricultural land
is virtually sterile with almost no butterflies.
In such situations, butterflies can survive
only on road verges, in remaining nature
reserves and urban areas. In these countries
the biggest loss of butterflies probably
occurred before the start of the Butterfly
Monitoring Schemes in the 1980s and 1990s.
As a result butterfly populations in these
areas are at a low level and are vulnerable to
further losses of sustainably managed
grassland or fragmentation.

Abandonment
In recent decades large areas of grassland
have become abandoned, especially in areas
that are too wet, steep, rocky or otherwise
unsuitable for intensive farming.
Furthermore, many villages in the European
countryside have become abandoned for
social reasons, often leading to young
people moving to cities and only old people
remaining. Following abandonment, some
butterfly species flourish for a few years
because of the lack of management, but
thereafter scrub and trees invade and the
grassland disappears, including its rich flora
and butterfly fauna. At the end scrubland
and forest remains only, leaving no room for
grassland butterflies.
Photo: Kars Veling
Intensification and abandonment are the main drivers for the decline of grassland butterflies in Europe.
Left: intensification leads to sterile grasslands, where there is no room for butterflies. Right: after abandonment butterflies can
flourish for a few years before scrubs and trees invade and the grassland also become unsuitable for grassland butterflies.
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Intensification is the most important threat
to butterflies on the relatively flat areas of
the ‘old-EU’, ranging from the eastern half
of the UK over the north of France, Belgium,
Apart from intensification and abandonment fragmentation
Netherlands, Northern Germany and
and climate change have an impact on grassland butterflies.
Denmark, as well as in flat areas in the other
In some regions habitats have been destroyed by urbanisation.
parts of Europe. This trend may soon extend
into parts of Poland as well. In contrast,
makes it more difficult for butterflies to reabandonment and lack of sustainable grazing is
colonise if they become locally extinct.
the chief threat in Southern and Eastern Europe,
where the land is often mountainous or rocky
Climate change is also expected to have a
and the soils relatively poor.
serious effect on the distribution and population
sizes of grassland butterflies in the future as
In addition to these two main drivers, there are
grasslands face extreme weather events such as
other threats to grassland butterflies in Europe,
droughts or fire, or change their composition. In
including fragmentation and climate change. The
montane habitats, as temperatures rise,
intensification and abandonment of grassland
sensitive butterfly species may not be able to
leads to the fragmentation and isolation of the
move to higher altitudes as there may be no
remaining patches. This not only reduces the
further land to colonise or no suitable grassland
chances of survival of local populations but also
habitat there.
This Purple-edged Copper (Lycaena hippothoe)
is
DE VLINDERSTICHTING
2010 | The European Butterfly Indicator for Grassland species 1990-2009
another wet-grassland butterfly that has declined
following intensification in Western Europe.
14
Chapter 6 / Implications
The European Grassland Butterfly Indicator shows that butterfly numbers on
grasslands have decreased by almost 70%. What can we do to stop further decline,
and how can we get these beautiful insects back to Europe’s meadows?
What does the European Grassland Butterfly Indicator tell us?
The European Grassland Butterfly Indicator
shows a strong negative trend (figure 4). The
indicator shows that since 1990 butterfly
populations have declined by almost 70%. Thus
the trend identified in the first two versions of
this indicator in 2005 and 2008 has not stopped,
but has continued (Van Swaay & Van Strien,
2005, 2008). This shows that butterflies are still
disappearing from Europe’s grasslands at an
alarming rate.
This huge decline has important implications to
the conservation of biodiversity because
butterflies are considered to be representative
indicators of trends observed in most other
terrestrial insects, which together form around
two-thirds of the world’s species (Thomas,
2005). Butterflies are therefore useful
biodiversity indicators, for example in evaluating
progress to the EU target of halting biodiversity
loss by 2010.
Butterflies appeal both to the general public and
decision-makers (Kühn et al., 2008). They are
also fairly easy to recognize and therefore data
on butterflies have been collected for many
years and by thousands of voluntary observers.
The method for monitoring butterflies is well
described, extensively tested and scientifically
sound (Pollard 1977; Pollard & Yates, 1993; Van
Swaay et al., 2008). As a result, butterflies are
the only invertebrate taxon for which it is
currently possible to estimate rates of decline
among terrestrial insects (de Heer et al. 2005;
Thomas 2005).
The The
Common
Common
BlueBlue
(Polyommatus
(Polyommatus
icarus)
icarus)
is still
is still
a a
widespread
widespread
andand
common
common
grassland
grassland
butterfly
butterfly
in most
in most
of Europe.
of Europe.
It shows
It shows
however
however
a significant
a significant
decrease.
decrease.
DE VLINDERSTICHTING 2010 | The European Butterfly Indicator for Grassland species 1990-2009
15
The Small Heath (Coenonympha pamphilus) is a
inconspicuous butterfly of grasslands throughout
Europe. It is declining in the EU and Europe.
Can the trend be reversed?
As the majority of grasslands in Europe require
active management by humans or sustainable
grazing by livestock, butterflies also depend on
the continuation of these activities. The main
driver behind the decline of grassland butterflies
is thought to be changes in rural land use. In
some regions, grassland habitats have
deteriorated due to agricultural intensification,
while in other regions (such as more remote
mountain areas) the main problem is land
abandonment. In both cases, the situation for
butterflies is the same, as their habitats become
less suitable for breeding. When land use is
intensified, host-plants often disappear or the
management becomes unsuitable for larval
survival. In the case of abandonment, the
grassland quickly becomes tall and rank, and is
soon replaced by scrub and eventually
woodland.
In some regions of North-western Europe, where
intensification is the main driver, grassland
butterflies are now almost restricted to
(rail)road verges, rocky or wet places, urban
areas and nature reserves. For the common and
widespread species verges can be an important
habitat, certainly if the management of these
areas consist of traditional mowing and hay
making.
Although the management of nature reserves is
mostly targeted at achieving a high biodiversity,
butterflies still suffer from fragmentation of
habitat. When a species disappears from a
locality, even if this is by natural causes, the site
often cannot be re-colonised, as the nearest
population is too far away. There are many
examples of such isolated grassland habitats
where species have disappeared one by one,
leaving an impoverished fauna.
In urban areas traditional lawn management can be changed
to a traditional hay making regime.
Where the right side of this lawn is managed by weekly
mowing, the left side is now full of flowers and rich in insects
and butterflies. Places like this are easy and cheap to create,
and can form a safe-haven for many widespread grassland
butterflies, like the Common Blue and Small Heath, thus
preventing their further decline.
DE VLINDERSTICHTING 2010 | The European Butterfly Indicator for Grassland species 1990-2009
16
This photo shows the two main causes
for the decline of grassland butterflies:
intensification and abandonment.
The dark green flat area in the
foreground is now under intense
agricultural use and unsuitable for
butterflies. In the hills in the background
the small semi-natural grasslands are
abandoned and slowly turn into forest.
Grassland butterflies are declining here
at an alarming rate. So although this
area is still rich in grassland butterflies, it
can be expected that many species will
disappear within the next years.
In order to achieve recovery it is urgent to stop
the loss in semi-natural grassland extent and
quality to sustain remaining butterfly
populations and provide a reservoir for recolonisation in adjacent areas of restored
habitat.
In the intensively farmed parts of the European
Union, the completion of the Natura 2000
network, as part of the Habitats (92/43/EEC)
and Species (79/409/EEC) Directive, is one of
the most important tools to prevent further loss
of grassland biodiversity. The network could
give could give a positive lead on the
conservation of the butterfly fauna of
grasslands. Of the species listed in the Annexes
of the Directive, three species were included as
specialist species in the European Grassland
Butterfly Indicator. One of them (Phengaris
nausithous, formerly Maculinea nausithous)
shows a decline, both in the European Union and
across Europe. The trend of Phengaris
(Maculinea) arion and Euphydryas aurinia is
uncertain. Although there are signs that directed
conservation effort can in some circumstances
reverse a negative trend for these species (e.g.
Wynhoff, 2001), it is also clear that small patches
supporting specialised species that are not part
of a wider metapopulation are very vulnerable
to local extinctions. If such sites are isolated
from nearby grasslands supporting healthy
butterfly populations, there is little chance of
recolonisation from surrounding or nearby
patches. This is often the case in an intensified
or abandoned landscape. Although the Natura
2000 network is vital to the survival of many
species, management must guard against losses
due to intensification and abandonment, and
this instrument must be seen in the context of
the wider landscape.
After abandonment scrubs and trees invade the
grasslands, leaving no room for grassland butterflies.
DE VLINDERSTICHTING 2010 | The European Butterfly Indicator for Grassland species 1990-2009
17
It is clear that, on its own, the Natura 2000
network will not be sufficient to halt the loss of
grassland butterflies. Additional measures are
needed urgently to encourage butterfly friendly
grassland management across the EU.
Abandonment is mostly caused by socioeconomic factors, leading to farmers giving up
marginal livestock farming and young people
moving to cities and other urbanised areas.
Often only older people remain in the villages,
and one by one grasslands become abandoned.
In other cases the landscape does not allow for
intensive farming, and as farmers feel they
cannot make a proper living, they leave the area,
abandoning the grasslands. The conservation of
grassland butterflies thus requires the creation
of a viable European countryside where people
can obtain sustainable livelihoods from grassland
farming. To stop abandonment, we need to give
farmers with High Nature Value farmland much
better support and give young farmers in these
areas a future, while at the same time respecting
long established farming traditions, as
prescribed by the geography and landscape.
Baldock et al. (1993) and Beaufoy et al. (1994)
described the general characteristics of lowinput farming systems in terms of biodiversity
and management practices and introduced the
term HNV farmland (High Nature Value
farmland). A first overview of the distribution of
HNV farmland in Europe has been produced by
Paracchini et al. (2008). Examples of high nature
value farmland areas are alpine meadows and
pasture, steppic areas in eastern and southern
Europe and dehesas and montados in Spain and
Butterflies are excellent indicators for biodiversity.
Male of the Small Copper (Lycaena phlaeas), one of the
species of the Grassland Butterfly Indicator.
Portugal. Such areas are vital for the survival of
grassland butterflies across Europe and their
maintenance provides the best long-term and
sustainable solution. This will require the
support of small farmers and their traditional
way of life over relatively large areas, so they do
not have to resort to intensification or
abandonment as their only options.
This will only be possible if there is a redirection
of some Common Agriculture Policy funding into
a new scheme to support such sustainable
management and livelihoods in HNV areas.
Butterflies as indicators
This indicator shows that there are huge changes
in butterfly diversity on European grasslands.
Incorporating butterflies in EU policy, as
described above, and monitoring the changes
with this indicator, is an important next step. We
urge the European Union to use the possibilities
of butterflies as indicators (not only for
grasslands, but also for other habitats), as it
makes a very good (and cheap) addition to the
existing bird indicators. Furthermore it gives a
deeper insight in the well being of not only
butterflies, but also other insects and small
animals.
Given the evidence of declines, we urge decision
makers to act swiftly to integrate biodiversity
concerns into sectoral policies and invest more
in habitat protection, restoration and recreation,
where feasible. The consequences of continuing
existing trends in land management will result in
further declines which in time will be
catastrophic for the whole food chain which
depends on invertebrates. EU Heads of
Government recently committed themselves to
avoiding such consequences and the time to act
is now.
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After a
grassla
Chapter 7 / How to continue with monitoring and indicator production?
Butterflies are among the few species groups where large scale, continent wide
monitoring is feasible. We urge the European countries, the EU and its institutes to
stimulate butterfly monitoring and secure butterfly indicators.
In this third version of the European Grassland
Butterfly Indicator, new countries have joined in
and thus the geographical scope of the indicator
is improving rapidly, especially in the EU. This
makes butterflies, after birds, the first group for
which European trends can be established and
used for the evaluation of biodiversity. From the
headline indicators which have been proposed
by the European Environment Agency (2007),
the bird and butterfly indicators are used in the
indicator ‘abundance and diversity of groups of
species’. This is in fact one of the few ‘direct’
core biodiversity indicators, as most of the
others represent pressures on biodiversity or
social responses to biodiversity loss (Levrel et al.,
2010).
Although this is already the third version of the
Grassland Butterfly Indicator, we are still in the
building phase. The construction of ad-hoc
indicators, as this and the two previous versions
of the Grassland Butterfly Indicator, leave no
room for the long term investments needed to
ensure continuity and further improvements in
indicator quality. In every updated version of the
European grassland butterfly indicator, new
countries join in and more ‘old’ data become
available. Furthermore the time-series that can
be used becomes longer, resulting in more
robust trends and smaller standard errors. As
new knowledge becomes available (e.g. the new
Red List for European Butterflies; Van Swaay et
al., 2010), this has an influence on the indicator.
This is an inevitable consequence of the
enlargement of the number of transects and
countries, as well as our knowledge, which
improves the quality of the indicator. The same
process has happened for the bird indicators.
However, the system of ad-hoc indicators, which
has been followed so far, is not a solid basis to
produce such important indicators. Therefore
the authors urge the EU to ensure proper and
structural funding to further develop the
indicators and their quality, thus ensuring a
robust product which can be used for multiple
purposes. Adding butterfly indicators to the
monitoring- and indicator programs of the EU
would also add the important group of insects to
the structural indicators of biodiversity.
The Chalkhill Blue (Polyommatus coridon) is one of
the indicator species of the European Grassland
Butterfly Indicator.
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Chapter 8 / Conclusions

This report gives an update of an indicator for Grassland Butterflies, which gives the trend of a
selection of butterflies characteristic of European grasslands.

The indicator is based on national Butterfly Monitoring Schemes from all over Europe, most of
them active in the European Union (see map 1).

Since 1990 the results show that the index of grassland butterfly abundance has declined by
almost 70%, indicating a dramatic loss of grassland biodiversity. Since the monitoring schemes are
biased towards natural and species-rich areas, this trend is probably conservative.

In North-western Europe intensification of farming is the most important threat to grassland
butterflies. Redirection of CAP funding to support sustainable farming of HNV areas is vital to
halting further losses and supporting some recovery.

The completion of the Natura 2000 network across Europe is an important way to help these
butterflies. In addition restoration or recreation of mosaics of habitats at a landscape scale are
needed.

In many parts of the rest of Europe, abandonment is the key factor in the decline of grassland
butterflies. Only if young farmers see a future for their families, while at the same time respecting
long established farming traditions, can grassland butterflies be saved. The support of HNV
farmland would be a critical way to achieve this.

The European Grassland Butterfly Indicator should become one of the headline indicators for
biodiversity in Europe. It should also be used as a measure of the success of agriculture policies.
Core funding of this and other butterfly indicators can guarantee the development of more robust
indices and their extension to other habitats. This would assist with the validation and reform of a
range of sectoral policies and help achieve the goal set by European Heads of Government to halt
biodiversity losses and by 2020 restore, in so far as feasible, biodiversity and ecosystems.
Semi-natural grasslands still support a wealth of butterflies. Respecting old farming traditions, while at the same time given young
farmers a future, is one of our challenges. The support of High Nature Value Farmland could be one of the ways to achieve this.
DE VLINDERSTICHTING 2010 | The European Butterfly Indicator for Grassland species 1990-2009
20
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Baldock D., Beaufoy G., Bennett G. & Clark, J. (1993). Nature conservation and new directions in the
common agricultural policy. IEEP London.
Beaufoy G., Baldock D. & Clark, J. (1994). The nature of farming. Low intensity farming systems in nine
European countries. Report IEEP/WWF/JNRC, London, Gland, Peterborough
De Heer, M., Kapos, V. & Ten Brink, B.J.E. (2005). Biodiversity trends in Europe: development and testing
of a species trend indicator for evaluating progress towards the 2010 target. Phil. Trans. R. Soc. B.
360, 297-308
European Environment Agency (2007). Halting the loss of biodiversity by 2010: proposal for a first set of
indicators to monitor progress in Europe. EEA, Copenhagen, 182 pp.
Gregory, R.D., Van Strien, A.J., Vorisek, P., Gmelig Meyling, A.W., Noble, D.G., Foppen, R.P.B. & Gibbons,
D.W. (2005). Developing indicators for European birds. Phil. Trans. R. Soc. B. 360, 269-288.
Kühn, E., Feldmann, R., Harpke, A., Hirneisen, N., Musche, M., Leopold, P. & Settele, J. (2008). Getting the
public involved in butterfly conservation: lessons learned from a new monitoring scheme in
Germany. Israel Journal of Ecology & Evolution 54, 89-103
Levrel, H., Fontaine, B., Henry, P-Y., Jiguet, F., Julliard, R., Kerbiriou, C., Couvet, D. (2010). Balancing state
and volunteer investment in biodiversity monitoring for the implementation of CBD indicators: a
French example. Ecological Economics 69, 1510-1586.
Maes, D. & Van Dyck, H. (2001). Butterfly diversity loss in Flanders (north Belgium): Europe's worst case
scenario? Biological Conservation 99 (3), 263-276
Pannekoek, J. & Van Strien, A.J. (2003). TRIM 3 manual. Trends and Indices for Monitoring data. CBS,
Statistics Netherlands, Voorburg, Netherlands.
Paracchini, M.L., Petersen, J.E., Hoogeveen, Y., Bamps, C., Burfield, I, Van Swaay, C.A.M. (2008). High
Nature Value Farmland in Europe. An estimate of the distribution patterns on the basis of land
cover and biodiversity data. European Commission, Joint Research Centre, Institute for
Environment and Sustainability.
Pollard, E. (1977). A method for assessing changes in the abundance of butterflies. Biological Conservation
12 (2), 115-134
Pollard, E. & Yates, T.J. (1993). Monitoring Butterflies for Ecology and Conservation. Chapman & Hall,
London.
Sutherland, W.J. (2006). Ecological Census Techniques. 2ndedition Cambridge University Press,
Cambridge.
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Thomas, J.A. (2005). Monitoring change in the abundance and distribution of insects using butterflies and
other indicator groups. Phil. Trans. Soc. B. 360, 339-357.
Van Swaay, C.A.M., Plate, C.L. & Van Strien, A. (2002). Monitoring butterflies in the Netherlands : how to
get unbiased indices. Proceedings of the Section Experimental and Applied Entomology of The
Netherlands Entomological Society (N.E.V.) 13, 21-27
Van Swaay, C.A.M. & Van Strien, A.J. (2005). Using butterfly monitoring data to develop a European
grassland butterfly indicator. In: Kuehn, E., Thomas, J., Feldmann, R. & Settele, J. (eds.) 2005.
Studies on the Ecology and Conservation of Butterflies in Europe. Proceedings of the Conference
held in UFZ Leipzig, 5-9th of December, 2005.
Van Swaay, C.A.M. & Van Strien, A.J. (2008). The European Butterfly Indicator for Grassland species: 19902007. Report VS2008.22 - De Vlinderstichting, Wageningen
Van Swaay, C.A.M.; Strien, A.J. van; Julliard, R.; Schweiger, O.; Brereton, T.; Heliölä, J.; Kuussaari, M.; Roy,
D.; Stefanescu, C.; Warren, M.S.; Settele, J. (2008). Developing a methodology for a European
Butterfly Climate Change Indicator. Report VS2008.40 - De Vlinderstichting, Wageningen
Van Swaay, C.A.M. & Warren, M.S. (1999). Red data book of European butterflies (Rhopalocera). Nature
and environment ; no. 99, Council of Europe Publishing, Strasbourg
Van Swaay, C.A.M., Warren, M.S. & Loïs, G. (2006). Biotope use and trends of European butterflies.
Journal of Insect Conservation 10 (2), 189-209
Van Swaay, C.A.M.; Cuttelod, A.; Collins, S.; Maes, D.; López Munguira, M.; Šašic, M.; Settele, J.; Verovnik,
R.; Verstrael, T.; Warren, M.; Wiemers, M.; Wynhoff, I. (2010). European Red List of butterflies.
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Thesis Wageningen University.
DE VLINDERSTICHTING 2010 | The European Butterfly Indicator for Grassland species 1990-2009
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Annex I / Butterfly Monitoring Schemes in the indicator
Since the start of the first Butterfly Monitoring Scheme in the UK in 1976 more
and more countries have joined in. This annex summarizes the most important
features of the schemes used for the European Grassland Butterfly Indicator.
Field methods
All schemes apply the method developed for
the British Butterfly Monitoring Scheme
(Pollard & Yates, 1993). The counts are
conducted along fixed transects of 0.5 to 3
kilometres, consisting of smaller sections,
each with a homogeneous habitat type, but
the exact transect length varies among
countries. The fieldworkers record all
butterflies 2.5 metres to their right, 2.5
metres to their left, 5 metres ahead of them
and 5 metres above them (Van Swaay et al.,
2002). Butterfly counts are conducted
between March-April to September-October,
depending on the region. Visits are only
conducted when weather conditions meet
specified criteria. The number of visits varies
from every week in e.g. the UK and the
Netherlands to 3-5 visits annually in France
(table 2).
special protected areas. In the older schemes,
such as in the UK and the Netherlands, but
also in the recently established scheme in
Germany, transects were selected by free
choice of observers, which in some cases has
led to the overrepresentation of protected
sites in natural areas and the undersampling
of the wider countryside and urban areas
(Pollard & Yates, 1993), while in Germany this
effect was not that pronounced (Kühn et al.,
2008). Obviously, in such a case the trends
detected may be only representative for the
areas sampled, while their extrapolation to
national trends may produce biased results.
Such bias can however be minimized by poststratification of transects. This implies an a
posteriori division of transects by e.g. habitat
type, protection status and region, where
counts per transect are weighted according to
their stratum (Van Swaay et al., 2002).
Species set
Transect selection
To be able to draw proper inferences on the
temporal population trends at national or
regional level, transects should best be
selected in a grid, random or stratified random
manner (Sutherland, 2006). Several recent
schemes, e.g. in Switzerland and France, have
been designed in this manner (Henry et al.,
2005). If a scheme aims to monitor rare
species, scheme coordinators preferably
locate transects in areas where rare species
occur, leading to an overrepresentation of
The grassland indicator is based on seven
widespread grassland species (Ochlodes
sylvanus, Anthocharis cardamines, Lycaena
phlaeas, Polyommatus icarus, Lasiommata
megera, Coenonympha pamphilus and
Maniola jurtina) and ten grassland-specialists
(Erynnis tages, Thymelicus acteon, Spialia
sertorius, Cupido minimus, Phengaris arion,
Phengaris nausithous, Polyommatus bellargus,
Cyaniris semiargus, Polyommatus coridon and
Euphydryas aurinia).
DE VLINDERSTICHTING 2010 | The European Butterfly Indicator for Grassland species 1990-2009
23
10
7-10
65-67
15-20
9
ca 11
France
2005
549-660
4.2
v
p
v ~70%,
p ~30%
v
2001-2004
2005
2001
0
400
50
10-15
15-20
15-20
1989
50-87
2007
2009
2004
1998-2006
2007
1994
1998
1990
1990
1973 (1976)
France - Doubs
Germany
Germany - Nordrhein
Westfalen
Germany – Pfalz (Phengaris
nausithous only)
Ireland
Lithuania
Jersey
Portugal
Slovenia
Spain - Catalonia
Switzerland - Aargau
The Netherlands
Ukraine – Carpathians and
adjacent parts
United Kingdom
no
no
yes
no
no
no
yes
no
p
v
v
free
by co-ordinator
free for
volunteers
half random,
half free
by co-ordinator
free
free
yes
yes
no
no
yes
yes
1
p
by co-ordinator
yes
no
16-63
14
15
0
9-14
60-70
101-107
430
158
16.3
6-9
15-25
3-5
6.25 - 7.53
30
10
15-20
5 (2-10)
v
v
v
v
v
v
p
v
p
free
free
free
free
by co-ordinator
free
grid
free
free
yes
no
yes
no
yes
yes
yes
yes
yes
no
no
no
no
no
no
no
no
yes
819-977
19
v
free
yes
yes
Counts by
(v=volunteers,
p=professionals)
Nature reserves overrepresented*
Number of counts on a
transect per year
(average or range)
1991
2004
1999
Representative for
agricultural grasslands*
Number of transects per
year 2007-2009
Belgium - Flanders
Estonia
Finland
Method to choose sites
Starting year
Table 2: Characteristics of the Butterfly Monitoring Schemes used for the European Grassland Butterfly
Indicator.
*: assessed by experts opinion. In case a monitoring scheme is not representative for agricultural grasslands
and/or nature reserves are overrepresented, it means that the resulting trends may be biased towards nonagricultural areas (often nature reserves), where management is focussing on the conservation of biodiversity.
Such a scheme probably underestimates the (mostly negative) trend of butterflies in the wider countryside.
Butterflies are counted on fixed transects
and under
DE VLINDERSTICHTING 2010 | The European Butterfly Indicator for Grassland species 1990-2009
standardised weather conditions (which can be
summarised to: nice, sunny weather).
24
Annex II / Method
We used the following procedure to compute
the grassland indicator.
 The national coordinators of monitoring
scheme provided their count data. More
specific, we received yearly counts per site
per year in which the results of various
visits were aggregated. We used this to
calculate national indices for each species
for which monitoring data were available.
The indices were produced using Poisson
regression as implemented in the widely
used program TRIM (Pannekoek & Van
Strien, 2005). In addition to indices, TRIM
calculates overall slopes for the entire
time series available or selected parts of
the time series, such as from 1990
onwards.
 The national indices were checked on
reliability and magnitude of confidence
intervals. Indices were not used if the time
series were very short, based on few sites
or observations only or if standard errors
of the overall slopes were extremely large
(>0.5).
 To generate supra-national indices, the
differences in national population size of
each species in each country were taken
into account. This weighting allows for the
fact that different countries hold different
proportions of a species’ European
population (Gregory et al., 2005). But we
applied area weighting rather than
population weighting as in Gregory et al.
(2005), because no national population
estimates for butterflies are available. This
implies that we treated as weights the
proportions of each country (or part of the
country) in the European distribution of a
species (based on Van Swaay & Warren,
1999 and adapted according to Van Swaay
et al., 2010). The missing year totals in



particular countries with short time series
were estimated by TRIM in a way
equivalent to imputing missing counts for
particular transects within countries
(Gregory et al., 2005).
In this updated indicator, we also took
into account differences in the number of
visits and transect length between
schemes. Three different types of data
were received from the national
coordinators; (i) the average yearly
number across all visits per site, (ii) the
yearly sum of the number of individuals
seen during all visits as well as the
associated number of visits for each site
and (iii) the yearly sum of the number of
individuals seen during all visits but
without exact information on the number
of visits per site. The second data type was
made equivalent to the first data type by
applying 1/number of visits for each site
as weights in the calculation of national
indices. The third data type was made
equivalent by applying weights in the
calculation of the supranational indices.
These latter weights were based on the
estimated average number of visits and
the number of generations covered.
Differences in transect length were also
included in the weights in the calculation
of supranational indices. The weights to
account for the different number of visits
and transect length were then combined
with the area weights.
Species indices were combined in a
grassland indicator by taking the
geometric mean of the supranational
indices.
Few species had missing indices for some
years at the supranational level. These
DE VLINDERSTICHTING 2010 | The European Butterfly Indicator for Grassland species 1990-2009
25


were estimated using a chain index before
calculating the indicator.
Results of supranational indices per
species were checked on consistency with
national indices and results in Van Swaay
& Van Strien (2005; 2008). Supranational
indicators were compared with national
indicators to test if the supranational
indicators were mainly based on the
results of one or a few countries only. This
was not the case.
Trend classification: the multiplicative
overall slope estimate (trend value) in
TRIM (Pannekoek & Van Strien, 2003) is
used to classify the trend (table 1):
o Decline: significant decline where the
upper limit of the confidence interval
< 1.00
o Stable: no significant increase or
decline, and it is certain that the
trends are less than 5% per year.
o Uncertain: no significant increase or
decline, lower limit of confidence
interval <0.95 or upper limit >1.05.
Potential biases
Although the Butterfly Monitoring Schemes
are very similar, there are differences in
choice of location, number of counts,
corrections for unstratified sampling, etc.
These are summarised in Annex 1. These
changes can potentially lead to biases. It is
also important to note that in countries where
the choice of the location for the transect is
free (table 2), there is an oversampling in
species-rich sites, nature reserves or regions
with a higher butterfly recorder density. The
trend of butterflies within nature reserves
may be expected to be better than in the
wider countryside, since the management of
these reserves focuses on reaching a high
biodiversity and positive population trends.
This suggests that the grassland indicator is
probably a conservative measure of the real
trend across the European landscape. There is
a risk that the decline in the population size of
butterflies is actually more severe than the
indicator shows. We hope to be able to test
this in future.
The Large Blue (Phengaris arion), one of the indicator
species, is listed on annex II and IV of the Habitats
DE VLINDERSTICHTING 2010 | The European Butterfly Indicator for Grassland species 1990-2009
Directive.
26
Annex III / Improving the indicator and building other butterfly
indicators
This report presents the third version of the European Grassland Butterfly
Indicator. In this section we want to indicate important ways to further improve
the quality of the indicator and possibilities for new indicators.
Like the two previous versions, this Grassland
Butterfly Indicator was produced on an ad-hoc
basis. Although this works well as it is, there
are also some issues which could be improved
if more structural funding would become
available. Many of these would lead to the
same improvements as the bird indicators
have undergone. They include:
 A full and standardized quality control.
Although all controls have now been made
on an ad-hoc basis, this is relatively timeconsuming and offers the chance that
controls are forgotten or misinterpreted.
We would prefer to build a solid database,
in which all possible controls and
assessment could be standardized and
performed on demand. However this
involves a long term investment, although
it will be cheaper on the long run.
 As described in Annex II, national data are
weighted to build supra-national trend.
Besides a correction for the part of the
European distribution, corrections are
performed for the average length of a
transect (if transects in a country are much
longer than in others, the numbers have to
be downweighted), the number of counts
(if much more counts are made in one
country, the numbers have to be
downweighted) and the number of
generations – if the species has more than
one generation per year – (if the numbers
of two or three generations are added,
they have to be downweighted to compare
them with a country where only the data
of one generation are given). It would be
good to standardize the input as much as
possible and to perform the weighting as
much as possible per species (now often
per country). This can be build into a
database as a long-term investment.
 If the data needed to build the indicator
would be collected from the national coordinators at a more standardized way
every year (so not on an ad-hoc basis), the
preparation of new indicators could be
much more flexible. There is already good
evidence that butterflies are very suitable
to produce a European Butterfly Climate
Change Indicator (Van Swaay et al., 2008).
But also the preparation of a woodland,
heathland or wetland indicator would be
possible.
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